Problem: $\dfrac{4}{8} - \dfrac{1}{8} = {?}$
$ = {\dfrac{4 \times 1}{8 \times 1}} - {\dfrac{1 \times 1}{8 \times 1}} $ $ = {\dfrac{4}{8}} - {\dfrac{1}{8}} $ $ = \dfrac{{4} - {1}}{8} $ $ = \dfrac{3}{8}$